Process for purifying chloroform.



4 decinal or anesthetic purposes.

UNITED STATES PATENT onrron.

GUSTAVUS MICHAELIS, OF ALBANY, NEW YORK.

PROCESS FOR PURIFYIN G CHLOROFORM.

No Drawing.

To all whom it may concern:

'Be it known that I, GUSTAVUS Mlormnnrs, a citizen of the United States of America, residing at the city of Albany, in the county of Albany and State of New York, have invented a certain new and useful Process for Purifying Chloroform, of which the. following is a specification.

This invention relates broadly to 'the manufacture of purified chloroform from ordinary or impure chloroform obtained by the usual well-known methods.

Chloroform has been known for nearly one hundred years and it has been, and is at present, produced from a great many different bodies, of which the most important are alcohol, chloral, acetone, carbon-tetrachlorid, and aldehyde; but no matter from what source or starting material it may have been obtained, it always contains by-products or impurities so called, which should be eliminated before it can be used for me- The removal or destruction-of these impurities has always been a difiicult problem and it has heretofore only been possible to effect their partial elimination. The principal agent for.

I the removal of these impurities has been,

and is, concentrated sulfuric acid of 66? B. strength; for instance, distillation with or over sulfuric acid was resorted to, but it was found that this method yielded a chloroform which left, upon evaporation on blotting paper or otherwise, a disagreeable residual odor, which made it unfit for medicinal and especially anesthetic fpurposes. Then shaking of impure chloro orm with concentrated sulfuric acid of 66 B. at ordinary temperatures was recommended and it was made the ofiicial method published in the pharmacopoeias" of the United States and other countries. By this method, however, only those impurities are eliminated which can be destroyed by the action of cold sulfuric acid, leaving those impurities intact which are only acted upon or destroyed by hot sulfuric acid. The failure of either of these processes to give satisfactory results/is due to the fact that the action of sulfuric acid upon the impurities contained in the impure chloroform has heretofore not been understood. Sulfuric ,acid exerts a powerful action. upon many organic bodies, and while this action is strong at ordinary tempera- Specification of Letters Patent.

near its boiling point.

Patented Oct. 31, 1916.

Applicatibn filed July 12, 1916. Serial No. 108,877.

nets with the chloroform, all of which, withthe exception of chloroform itself, are acted upon by sulfuric acid. But I have found that there is a difference in its action. There are some impurities which are acted upon by sulfuric acid in the cold or at ordinary temperatiires, while others are only acted upon at higher temperatures or around the temperature of chloroform heated to or In order to obtain chloroform which is of ideal purity, it is necessary and essential A that the sulfuric acid, which is used when chloroform is treated with it in the cold, be removed as it contains all the impurities which can be acted upon, or they are destroyed, to a degree at least, by this cold sulfuric acid. If the used sulfuric acid is not removed and the chloroform is heated with the same sulfuric acid, this latter exercises a further decomposing influence upon the impurities which have been partly destroyed by the cold sulfuric acid, and it leaves the chloroform with an offensive odor. This point, that is, the careful removal of the sulfuric acid which contains the impurities destroyable by it .at ordinary temperatures, is the pivotal point upon which turns the eventual purity of the chloroform after having been subjected to the further action of sulfuric acid at the boiling temperature of chloroform, the reason being that the hot sulfuric acid exercises a further. decomposing action upon the by-products present in meters, the remaining ten cubic centimeters leave a disagreeable residual when evaporated upon blotting paper. This is the so; called odor test.

Second: When fifteen cubic centimetersof colorless, chemically. pure sulfuric acid are shaken with twenty cubic centimeters ofethis purified chloroform and eight drops of a forty per cent. solution of formaldehyde in furic acid of 66 the agitation is structed apparatus with thirty-three parts.

of cold, colorless, concentrated sulfuric acid of 66 Be. until a sample, after full separa tion from the now highly-discolored sulfuric acid, no longer imparts a color to colorless, chemically pure sulfuric acid when the same is vigorously shaken with it for at least five minutes, the proportion being about five cubic centimeters of sulfuric acid and fifty cubic centimeters of chloroform,

showing the removal of all impurities which can be eliminated by the action of cold sul- Bes strength. All of the highly-colored acid is now carefully removed from the chloroform and a new quantity of thirty-three per cent. of colorless sulfuric acid of 66 Be. is added to the chloroform while it still remains in the apparatus in which ithas been previously shaken with the acid. The mixture is then shaken while heat is applied to same until its temperature reaches or approaches the boiling point of chloroform, say 55 to C. It is kept at this temperature for three to four hours, the volatilized chloroform being condensed and returned to the apparatus either by means of a reflex cooler or by any other suitably constructed contrivance. The heating is then discontinued, but kept up for a further four to six hours until the mixture has cooled, when it is allowed to settle. The chloroform is then removed from the sulfuric acid and transferred to a tank in which it is repeatedly washed with water and a suitable alkali until it shows neutral with litmus paper to prove that the last traces of sulfuric acid have been removed. This done, the chloroform is transferred to a still and distilled over a dehydrating agent, such as calcium chlorid or potassium carbonate, or any other suitable agent. After the first ten parts of chloroform have distilled over, the receiver is changed and the next sixty to seventy parts of distillate as perfectly pure chloroform, left in the still is, the shaker, together with the first ten parts of distillate obtained, to be subjected again to the purifying treatment with an additional quantity of sulfuric acid of 66 B. and a new lot of impure chloroform. In other words, the results of the operation are from sixty to seventy parts of absolutely pure chloroform. It is well known that while what is are put away after cooling, returned to chemically pure chloroform does not keep unless from six-tenths to one per centum of absolute alcohol are added, and this must therefore be done at once to secure its stability. Chloroform which. has been treated as described is free from all impurities and will answer the most rigid tests which can be applied, to wit: First? If one hundred cubic centimeters of chloroform purified as described are evaporated on a water bath to ten cubic centimeters, the remaining ten cubic centimeters will leave no residual odor when volatilized upon blotting paper,the so-called odor test. Second: If fifteen cubic centimeters of colorless, chemically pure sulfuric acid are shaken with twenty cubic centimeters of chloroform, purified as described, and eight drops of a forty per cent. solution of formaldehyde in a glass stoppered cylinder, the sulfuric acid will not be discolored within one hour and will show only a faint discoloration after twenty-four hours, showing absence of all organic impurities,-the so-called formaldehyde sulfuric test. Third: If five cubic centimeters of colorless, chemically pure sulfuric acidare shaken for five minutes with fifty cubic centimeters of thus purified chloroform in a glass stoppered cylinder, neither the chloroform nor the sulfuric acid will show a discoloration after from twentyfour to forty-eight hours.

An example of carrying out the described process is the following: 1710 pounds of impure chloroform and 570 pounds of sulfuric acid of 66 Be. are placed in a suitable apparatus and are agitated for about four hours. The mixture is then allowed to settle for one and one-half hours, when the now highly-discolored acid is drawn off, taldng gare to remove it all as completely as possi- 1e. chloroform is charged anew with 57 0 pounds of sulfuric acid of 66 Be. and a second agitation is started, but the mixture is now heated to a temperature of from between 55 to 60 C. This shaking and heating is kept up for about four hours when the heat is withdrawn, and after further agitation for about six hours the agitation is stopped and the mixture is allowed to cool and to separate. After this is done the supernatant The apparatus still containing the chloroform is drawn ofl and transferred to a the formaldehyde sulfuric acid test. 1400 pounds of main portion, standing both the odor and formaldehyde-sulfuric acid tests. 200 pounds (about) left in still, to be reworked together with the first hundred pounds of slightly impure choloroform reected .as unfit for use at the beginning of the distillation. The'HOO pounds of absolutely pure chloroform obtained are immediately mixed with six-tenths to one per centum of absolute alcohol to insure its keeping qualities.

What I claim as my invention and desire to secure by Letters Patent is:

1. The process of purifying chloroform, comprising shaking together one hundred parts of chloroform and thirty-three parts of sulfuric acid of 66 B. placed in a suitable receptacle, until a sample, after full separation from the now highly-discolored sulfuric acid, no longer imparts a color to colorless, chemically. pure sulfuric acid when the same is vigorously shaken with it for at least five minutes, then removing the highlycolored acid from the chloroform and adding a new quantity of thirty-three parts of colorless sulfuric acid of 66 B. to the chloroform, shaking the mixture and applying heat thereto until its temperature reaches or approaches the boiling point of chloroform, condensing the volatilized chloroform and returningit to the mixture, then discontinuing the heat, but continuing the agitation for a time and allowing the mixture to settle and to cool, withdrawing the chloroform from the sulfuric acid, treating it with a suitable alkali until the last traces of sulfuric acid have been removed, then dehydrating the same and placing it in a still, distilling the chloroform and after c0llecting the perfectly pure chloroform adding to it for preserving it, absolute alcohol.

2. The process of purifying chloroform, comprising placing in a suitable receptacle one hundred parts of chloroform with thirtythree' parts of colorless, concentrated sulfuric acid and agitating the mixture, removing from the chloroform the acid which has become highly discolored after agitation for a suilicient length of time, then adding a new quantity of thirty-three parts of colorless, concentratedsulfuric acid, agitating the mixture and applying heat thereto until the mixture reaches substantially the boiling point ofchloroform, condensing the vapor and returnin it to the mixture in liquid form, continuing the agitation and recondensation of the vapors, then, after cooling, removing, washing and dehydration of the chloroform, subjecting the same to distillation, rejecting the first tenparts of distillate as slightly impure chloroform and collecting the next sixty to seventy parts as pure chloro form, adding to same from six-tenths to one per cent. of alcohol for preservation.

In testimony whereof I have aflixed my signature in presence of two witnesses.

GUSTAVUS MICHAELIS.

Witnesses:

BEULAH CABLE, FREDERICK W. CAMERON.

copies of this patent may be obtained for five cents each, by addressing the "Commissioner of Patents,

' Washington, D. G. 

